The present invention relates to a device for supplying gas into water combined with a water inlet arrangement. This can be used in tanks, ponds and sea cages.
In aquaculture it is important that the content of dissolved oxygen in the water is kept optimal. This is necessary for the health and the growing of the fish. Because the solubility of gases in water is reduced by increasing the temperature while the oxygen need of the fish is increasing at high temperature, there is a particularly great need for oxygen in warm periods. Increasing the capacity of oxygen dissolvers is, therefore, highly useful for the fish farmer. In addition, most of the fish hatcheries produce more fish per liter water than the installation originally was dimensioned. The amount of water is, therefore, the limiting factor of the installation. A better utilization of the water, a higher consumption of the oxygen and an improved dissolving capacity are therefore required.
Most hatcheries use pressurized oxygen dissolvers with a working pressure of 1-4 bars. By small amounts of water, it is normal to let all of the water flow go through the dissolver, but most commonly there is an outlet leading a part of the flow from the main pipe to a booster pump which pressurizes the dissolver. The oxygenated water is thereafter led back to the main pipe where it is mixed with untreated water. Most dissolving systems use 0-2.5 kWh per kilo O2 dissolved, depending on efficiency and available water pressure.
US 2005/0275119A1 and the related EP 1 598 106 A3 describe an oxygenating nozzle unit for the injection of gas in a liquid flow. The arrangement can for example be mounted on any pipe transporting liquid and with a need for the supply of gas, for example on the pipe supply to the basin for the farming of fish, on the pipe after circulation pump on a boat for live fish transportation, on the pipe after a circulation pump for vehicles for live fish transportation, on the pipe after a circulation pump on a container, or other arrangement for live fish transportation or on pressurized dissolvers for increasing the oxygenating capacity. The known venturi system generates micro bubbles in sea water. By the means of gas diffusion and redistribution of dissolved gas components in water, one can dissolve and add gas at a very low pressure, preferred for sea water applications.
EP 2 008 513 A1 discloses a water inlet arrangement for the use in fish tanks in aquaculture with a pipe to feed water into the tank, whereby the pipe has a plurality of openings. For a better adjustment of the flow a surrounding second element, having a plurality of openings, and/or a fixed or adjustable shield are provided.
This arrangement improves the water circulation in the tank. The document is silent about where and how the oxygen is supplied.
The not yet published European application 08022177.3 proposes a device for supplying gas into water in sea cages, tanks or ponds with a submerged pump and a dissolver for the gas. The oxygen enriched water is fed into the sea cage/tank/pond by a “normal” nozzle, a tube with holes or a perforated hose.